vitest-testing
Vitest testing framework patterns and best practices. Use when writing unit tests, integration tests, configuring vitest.config, mocking with vi.mock/vi.fn, using snapshots, or setting up test coverage. Triggers on describe, it, expect, vi.mock, vi.fn, beforeEach, afterEach, vitest.
- Installs
- 467
- Last 24h
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- Trending rank
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- Security
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Install
Works with every agent the skills CLI supports.
npx skills add https://github.com/existential-birds/beagle --skill vitest-testing- 01
Install
Run the command in your project. The CLI asks which agents to install for.
- 02
Describe the task
Ask your agent for something this skill covers. It loads vitest-testing automatically when relevant.
- 03
Review the result
The agent follows the SKILL.md steps, scripts and references bundled with the skill.
SKILL.md
The instructions your agent reads when the skill is triggered.
Vitest Best Practices
Quick Reference
import { describe, it, expect, beforeEach, vi } from 'vitest'
describe('feature name', () => {
beforeEach(() => {
vi.clearAllMocks()
})
it('should do something specific', () => {
expect(actual).toBe(expected)
})
it.todo('planned test')
it.skip('temporarily disabled')
it.only('run only this during dev')
})
Common Assertions
// Equality
expect(value).toBe(42) // Strict (===)
expect(obj).toEqual({ a: 1 }) // Deep equality
expect(obj).toStrictEqual({ a: 1 }) // Strict deep (checks types)
// Truthiness
expect(value).toBeTruthy()
expect(value).toBeFalsy()
expect(value).toBeNull()
expect(value).toBeUndefined()
// Numbers
expect(0.1 + 0.2).toBeCloseTo(0.3)
expect(value).toBeGreaterThan(5)
// Strings/Arrays
expect(str).toMatch(/pattern/)
expect(str).toContain('substring')
expect(array).toContain(item)
expect(array).toHaveLength(3)
// Objects
expect(obj).toHaveProperty('key')
expect(obj).toHaveProperty('nested.key', 'value')
expect(obj).toMatchObject({ subset: 'of properties' })
// Exceptions
expect(() => fn()).toThrow()
expect(() => fn()).toThrow('error message')
expect(() => fn()).toThrow(/pattern/)
Async Testing
// Async/await (preferred)
it('fetches data', async () => {
const data = await fetchData()
expect(data).toEqual({ id: 1 })
})
// Promise matchers - ALWAYS await these
await expect(fetchData()).resolves.toEqual({ id: 1 })
await expect(fetchData()).rejects.toThrow('Error')
// Wrong - creates false positive
expect(promise).resolves.toBe(value) // Missing await!
Quick Mock Reference
const mockFn = vi.fn()
mockFn.mockReturnValue(42)
mockFn.mockResolvedValue({ data: 'value' })
expect(mockFn).toHaveBeenCalled()
expect(mockFn).toHaveBeenCalledWith('arg1', 'arg2')
expect(mockFn).toHaveBeenCalledTimes(2)
Verification gates
Use this sequence when you add or change tests; each step has an objective pass condition.
- Run the test suite — From the package or workspace root, run the same command CI uses (check
package.jsonscripts; oftenvitest run,pnpm test, ornpm test). Pass: exit code is 0 and the report shows zero failing tests. - Async matchers — Pass: every
expect(…).resolvesandexpect(…).rejectsis prefixed withawait(await expect(...)), as in Async Testing. A line whereresolvesorrejectsappears withoutawaitfails this gate.
Additional Documentation
- Mocking: See references/mocking.md for module mocking, spying, cleanup
- Configuration: See references/config.md for vitest.config, setup files, coverage
- Patterns: See references/patterns.md for timers, snapshots, anti-patterns
Test Methods Quick Reference
| Method | Purpose |
|---|---|
it() / test() | Define test |
describe() | Group tests |
beforeEach() / afterEach() | Per-test hooks |
beforeAll() / afterAll() | Per-suite hooks |
.skip | Skip test/suite |
.only | Run only this |
.todo | Placeholder |
.concurrent | Parallel execution |
.each([...]) | Parameterized tests |
FAQ
What does the vitest-testing skill do?
Vitest testing framework patterns and best practices. Use when writing unit tests, integration tests, configuring vitest.config, mocking with vi.mock/vi.fn, using snapshots, or setting up test coverage. Triggers on describe, it, expect, vi.mock, vi.fn, beforeEach, afterEach, vitest.
How do I install vitest-testing?
Run npx skills add https://github.com/existential-birds/beagle --skill vitest-testing in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/vitest-testing/ (personal) or .claude/skills/vitest-testing/ (project).
Which AI agents can use vitest-testing?
Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.
Is vitest-testing safe to install?
No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.
Who maintains vitest-testing?
It is published by existential-birds in existential-birds/beagle. It has 467 recorded installs.
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